The fuel core for a nuclear reactor requires periodic replacement and a significant and critical aspect of nuclear power plant operation is the removal of a depleted fuel core assembly and the replacement thereof with a new fuel assembly. Within selected fuel assemblies are incore detectors that require removal and storage, such as by the use of cutting and shear apparatus, wherein the resultant smaller parts are placed within storage containers for removal and storage. Of course, due to the radioactivity of the fuel core components extreme care must be exercised in the processing and handling of the core components during preparation for storage, and it is common practice to disassemble the core while the components are submerged in the usual borated water shield in which the reactor is normally located.
Among the fuel core components which are to be stored are incore detector cables which are approximately 35 feet long and 7/32 inches in diameter. These cables are radioactive and it has been the usual practice to employ a manual hydraulically operated cutter to cut the cable into short pieces for storage in a cask. As the operation of the hydraulic cutter must take place underwater the manual cutting of the incore detector cables are difficult, inefficient and time consuming, and because of the problems encountered the volume of the storage container was not efficiently utilized.
It is an object of the invention to provide apparatus for automatically severing incore detector cables as used with nuclear reactor fuel assemblies into short lengths for waste storage purposes wherein the apparatus is capable of being operated while submerged in a water shield pool.
Another object of the invention is to provide apparatus for severing radioactive incore detector cables into short lengths for storage purposes wherein the apparatus is self-contained, except for an external electrical power source, and the operation is automatic and self-synchronized, and a high degree of skill on the part of the operator is not required.
A further object of the invention is to provide apparatus for shearing incore detector cables into short lengths for storage purposes wherein a single electric motor is used to intermittently drive feed rollers which feed the cable into a synchronized shear, the utilization of common driving means for the feed rollers and shear assuring proper synchronization between cable advancing and cutting.
Yet another object of the invention is to provide a cutter for incore detector cables wherein electric motor driven feed rollers intermittently advance the cable into a shear, and the motor may be reversed to permit an enlarged end of the cable to be removed from the apparatus.
The apparatus of the invention includes a base upon which both the cable cutting mechanism is supported as well as the disposable cask liner receiving the severed cable lengths. The entire apparatus may be lowered as a unit into the water-filled reactor cavity whereby the apparatus will be submerged in approximately 25 feet of borated water which functions as a shield. The shearing apparatus includes a watertight housing in which an electric motor is located having a vertically oriented drive shaft. The motor shaft drives a speed reduction transmission having an output shaft with which a Geneva intermittent drive transmission is associated, as is the eccentric crank structure which operates the shear.
The Geneva drive mechanism indexes a feed roller assembly located exteriorly of the motor and transmission casings whereby feed rollers intermittently rotate to feed the cable to be severed into the shear structure located below. A feed funnel located above the feed rollers aids in aligning and feeding the cable into the roller apparatus, and the movement of the cable during cutting is downward, the storage cask liner being located directly below the shear.
The incore detector cable is handled by gripping devices attached to the end of a pole, and the end of the cable is aligned with the feed funnel for reception into the feed roller assembly. As the feed rollers intermittently rotate and feed the cable into the shear each cycle of the shear will sever a 4" cable length which falls into the cask liner. The "upper" or "rear" end of the incore detector cable contains a seal plug and connector which is of such dimension as to not be capable of passing through the feed rollers and the last two feet of the cable are removed from the cutting apparatus be reversing the direction of rotation of the drive motor and this end portion of the cable is dropped into the cask liner without passing through the shear. After the cable shearing operation is completed the entire assembly, including cask liner, is removed from the reactor cavity pool, and the cask liner is removed from the apparatus base and processed for permanent storage.